1. Field of the Invention
The present invention relates to a device for applying an auxiliary film to an elongate continuous slide fastener chain in an area where a separable end stop will be attached during a process of manufacturing a separable slide fastener
2. Description of the Prior Art
Separable slide fasteners are successively manufactured from an elongate continuous slide fastener chain by processing the slide fastener chain in successive steps. The slide fastener chain comprises a pair of slide fastener stringers composed of two stringer tapes and a pair of intermeshing rows of coupling elements mounted on respective longitudinal inner edges of the stringer tapes. In one processing step, element-free spaces are defined in the rows of coupling elements at equally spaced intervals. In a subsequent processing step, an auxiliary film of thermoplastic synthetic resin is ultrasonically applied or fused to the stringer tapes across one of the element-free spaces near one end thereof. One known device for applying such an auxiliary film intermittently feeds the slide fastener chain in one horizontal direction. While the slide fastener chain is being fed along, a stopper is inserted into the element-free space to stop the slide fastener chain, and then an elongate auxiliary film is supplied to a position above a movable anvil disposed below the slide fastener chain in vertical alignment with an ultrasonic horn fixedly located over the slide fastener chain. Then, the anvil is moved upwardly to press the slide fastener chain against the ultrasonic horn, cut off the elongate auxiliary film into a predetermined film piece, and then fuse the film piece to the slide fastener chain with ultrasonic energy generated by the ultrasonic horn.
The elongate auxiliary film is supplied from a film roll by a feed roller and a presser roller which grip the film therebetween. The elongate auxiliary film is fed a desired length in each feeding cycle by controlling the rotation of the feed roller. Even if the auxiliary film on the film roll is used up or the auxiliary film fails to be fed for some reasons, the anvil is elevated against the slide fastener chain with no film piece therebetween. When this happens, a slide fastener chain length is fed along with no auxiliary film piece applied thereto.